I'm on 106. If I update to 107, can I continue using my project (with many artboards) or will I have to start something new?
Top level frames behave just like artboards. So if you have been using artboards not much should change.
I'll phrase it another way: When you open a project from pre-107, does it throw a warning in any way, or offer 'Cancel / Try' modal?
If it doesn’t show a modal in 106 it won’t show it in 107. We didn’t introduce any breaking changes with the vector release.